1. Field of the Invention
This invention relates generally to watertight electrical connectors for underwater service and more particularly to an improvement in the watertight integrity of such connectors.
2. General Background
Electrical connectors used in an underwater environment are subjected to stress, especially when used in deep water or in seismic exploration where high pressure, explosive forces, and underwater hazards can cause the connectors to leak, thus causing failure of the electrical connection. Connector failure due to leakage can cause the entire system to fail as a result of loss of watertight integrity within the electrical cable. Most underwater cable connectors utilized in the prior art recognize the need to protect the connectors from high pressure, potential connector separation, and absorption of explosive impact pressure by providing impact absorbing materials molded in place around the cable jackets and the connector pins. Various methods have also been employed in sealing the connector pins themselves as disclosed in U.S. Pat. Nos. 5,120,268, 5,387,119, 5,595,497, and 5,641,307. The U.S. Pat. No. 5,595,497 patent discloses a central core molded around the pins and enclosed within a relatively soft plastic body. The soft body is molded around the wires attached to the pins and also extends over a portion of the electrical cable jacket. It is further disclosed that the central core should be bonded, during the molding process, to the soft body, thus, at least in theory, providing a watertight seal between the open face of the connector's pins and the wiring connections. However, in reality, if the central core does not form a complete bond with the body, leaks can occur under high pressure. Further, no steps are taken to insure a bond between the individual wiring dielectric insulation or sheath and the molded soft body. In many cases, the molding material and the wiring insulation material are dissimilar and therefore do not bond. Wiring conductor insulation is often a thermoplastic material, such as polypropylene, which provides excellent dielectric qualities at an economical cost and prevents the electrical conductors from adhering together under heat and pressure during manufacture and storage. However, the thermoplastic polypropylene, used as a molding material in the connectors discussed above does not allow the two materials to bond without the introduction of a chemical bonding agent. It has also been observed that extreme care must be taken to insure that the polyurethane molded body material always forms a complete fill around the wiring connection to the connector's pins. Others have observed this problem and have attempted to solve the problem for a particular need, such as that disclosed by U.S. Pat. No. 5,776,564 which addresses the problem of bonding a polyamide-based mixture for its connector body to a polytetrafluoroethylene wiring insulation by coating the insulation with a thermoplastic elastomer on a polyester basis. This process, while allowing a chemical bond between the two components is only useful with specific wire coatings and then only with a specific body matrix. There is no proof that the process mentioned by the U.S. Pat. No. 5,776,564 disclosure will provide a chemical bond with any and all combinations of thermoplastic material nor does it purport to provide a water proof seal. Therefore, several claims were made to include various combinations, none of which include the use of polyurethane or the process of multiple removable sheaths as disclosed herein.
Connectors which are principally used under water and subjected to high pressure and continuous heavy abuse must insure watertight integrity. Further, the process of insuring comparability must be uniform without the need for chemical analysis of each component during the molding process.
It therefore follows that, if a tear or rip in the cable jacket occurs adjacent the cable connector, water is allowed to enter the cable under pressure and migrate along the conductors sheaths. If no permanent seal exists between the wiring insulation and the molded connector, water is allowed to ultimately reach the connector pin connection, in which case a short circuit occurs between the affected pins. Further, water may also be forced into whatever the cable and its connector is attached to opposite the connector, such as a main cable splice, thus affecting other connectors fixed thereto, which may result in catastrophic failure of the entire system.
If an incomplete fill occurs during molding of the connector, a void may develop which may fill with water due to leakage, thus causing a direct short circuit between the pins or at least a reading to ground.